Introduction and objective:
The COVID-19 pandemic causes vital concerns due to the lack of proved, effective, and safe therapy. Chloroquine and hydroxychloroquine seem to be useful, but recently serious concerns regarding their adverse events have risen. The aim of the study was to broaden the general perspective of chloroquine and hydroxychloroquine use in COVID-19 treatment, based on an analysis of their current safety profile among patients with rheumatic diseases.

Material and methods:
The study was based on a group of 152 patients with rheumatic diseases, aged 20–78 years, treated either with chloroquine or hydroxychloroquine. Analyzed data included age, gender, comorbidities, type of drug, dosage, treatment duration, and reported adverse events. Cases of drug withdrawal related to adverse events were also recorded.

Results:
The dosage was consistent in both groups: 250 mg of chloroquine or 200 mg of hydroxychloroquine daily. 77.6% of patients did not experience any adverse reactions to the treatment. Hydroxychloroquine showed better safety profile, with 10.9% of patients reporting side-ffects, compared to 28.9% in patients treated with chloroquine. The overall incidence of ophthalmic complications was 6.6%. For both drugs, no statistically significant correlation between adverse events and age, chronic heart or liver disease, or hypertension was found.

Conclusions:
Chloroquine and hydroxychloroquine at lower doses, as used in rheumatic diseases, prove to be relatively safe. Data from the literature show that high dosage as recommended in COVID-19 treatment may pose a risk of toxicity and require precise management, but prophylactic, long-term use of lower, safe doses might be a promising solution.